Two ways:
1) Find people already working on a game and ask how you can help. Learn how to do whatever they tell you they need.

2)Make a simple one from scratch by yourself. Playtest it with everyone you know. Make the easy fixes. Then take what you learned and make a better game, but stay simple. Build yourself a reputation among those who know you as the gal/guy who makes games.

Then recruit people to team up with you. If they don't know how to do anything, teach them. Ideally recruit them for the tasks you don't enjoy as much. Learn how to keep them motivated.

Here are some tools that make it easy to make games from scratch:
I started with RPGMaker XP. It's UI is extremely intuitive and it's especially great for JRPGs.

GameMaker is also a good tool for quickly making games. Not as intuitive as RPGMaker, but more flexible and still extremely easy to use.

In terms of programming, it's pretty easy to make 2d games in Flixel. Unity or Blender are good for 3d games--though these are slightly more complicated to make than 2d games.